This invention related to electronic printers and particularly to methods and means for preparing and processing a plurality of data concurrently originated by a keyboard or available from a plurality of sources prior to application to the printer to control printing of desired characters.
In the field of printers, characters are printed in response to input data available from a plurality of sources such as a keyboard, tape reader, answerback option or other sources such as CRT's, computers, etc. The data is generally available in the form of binary coded digital signals representative of characters to be printed or control functions to be executed. The control functions are related to proper printing operation and include such functions as line feed, carriage return, etc. In normal or usual operations, no problems are encountered because each character of data is available separately for utilization by the printer. Problems occur when a plurality of characters are concurrently available from a plurality of sources feeding into a common printer. The problem is complicated by the fact that since the individual bits associated with a particular character are of finite duration, the overlap of bits corresponding to different characters can lead to the printing of incorrect characters or to the loss of characters in the printout.
The problems become further complicated when it is desirable to synchronize signals available from individual sources which may change at any instant of time to a system wherein all signals may change only at discrete time intervals such as in a dynamic logic arrangement. Further difficulties arise when transferring a group of related bits of information from one part of a circuit to another. The transfer may be parallel, each data bit being presented simultaneously on separate lines. It may be serial in which all bits are presented on the same line one at a time. If more than one data source is active on the data line at one time, a merging of data may result, thereby destroying that data.
Accordingly, it is one object of this invention to provide an improved arrangement for utilizing data available from a plurality of sources in a simple and efficient manner.
It is a further object of this invention to provide an improved system whereby a group of asynchronous signals may be synchronized to the dynamic logic used in printer operation without the use of special or multiple synchronizing circuits.
It is a further object of this invention to provide a system of data transfer which is serial, whereby several data sources may be placed on one data line. These data sources are assigned a priority sequence such that no data merging may occur.
A further object of this invention is to provide an improved processing arrangement for use with digital data.